The present invention pertains to organometallic compounds and efficient organic light emitting devices comprising the same.
Research Agreements
The claimed invention was made by, on behalf of, and/or in connection with one or more of the following parties to a joint university-corporation research agreement: Princeton University, The University of Southern California, and the Universal Display Corporation. The agreement was in effect on and before the date the claimed invention was made, and the claimed invention was made as a result of activities undertaken within the scope of the agreement.
Electronic display currently is a primary means for rapid delivery of information. Television sets, computer monitors, instrument display panels, calculators, printers, wireless phones, handheld computers, etc. aptly illustrate the speed, versatility, and interactivity that is characteristic of this medium. Of the known electronic display technologies, organic light emitting devices (OLEDs) are of considerable interest for their potential role in the development of full color, flat-panel display systems that may render obsolete the bulky cathode ray tubes still currently used in many television sets and computer monitors.
Generally, OLEDs are comprised of several organic layers in which at least one of the layers can be made to electroluminesce by applying a voltage across the device (see, e.g., Tang, et al., Appl. Phys. Lett. 1987, 51, 913 and Burroughes, et al., Nature, 1990, 347, 359). When a voltage is applied across a device, the cathode effectively reduces the adjacent organic layers (i.e., injects electrons) and the anode effectively oxidizes the adjacent organic layers (i.e., injects holes). Holes and electrons migrate across the device toward their respective oppositely charged electrodes. When a hole and electron meet on the same molecule, recombination is said to occur and an exciton is formed. Recombination of the hole and electron in luminescent compounds is accompanied by radiative emission, thereby producing electroluminescence.
Depending on the spin states of the hole and electron, the exciton which results from hole and electron recombination can have either a triplet or singlet spin state. Luminescence from a singlet exciton results in fluorescence whereas luminescence from a triplet exciton results in phosphorescence. Statistically, for organic materials typically used in OLEDs, one quarter of the excitons are singlets and the remaining three quarters are triplets (see, e.g., Baldo, et al., Phys. Rev. B, 1999, 60,14422). Until the discovery that there were certain phosphorescent materials that could be used to fabricate practical electro-phosphorescent OLEDs (U.S. Pat. No. 6,303,238) and, subsequently, demonstration such that electro-phosphorescent OLEDs could have a theoretical quantum efficiency of up to 100% (i.e., harvesting all of both triplets and singlets), the most efficient OLEDs were typically based on materials that fluoresced. Fluorescent materials luminesce with a maximum theoretical quantum efficiency of only 25% (where quantum efficiency of an OLED refers to the efficiency with which holes and electrons recombine to produce luminescence), since the triplet to ground state transition of phosphorescent emission is formally a spin forbidden process. Electro-phosphorescent OLEDs have now been shown to have superior overall device efficiencies as compared with electro-fluorescent OLEDs (see, e.g., Baldo, et al., Nature, 1998, 395, 151 and Baldo, e.g., Appl. Phys. Lett. 1999, 75(3), 4).
Due to strong spin-orbit coupling that leads to singlet-triplet state mixing, heavy metal complexes often display efficient phosphorescent emission from such triplets at room temperature. Accordingly, OLEDs comprising such complexes have been shown to have internal quantum efficiencies of more than 75% (Adachi, et al., Appl. Phys. Lett., 2000, 77,904). Certain organometallic iridium complexes have been reported as having intense phosphorescence (Lamansky, et al., Inorganic Chemistry, 2001,40, 1704), and efficient OLEDs emitting in the green to red spectrum have been prepared with these complexes (Lamansky, et al., J. Am. Chem. Soc., 2001, 123,4304). Red-emitting devices containing iridium complexes have been prepared according to U.S. Application Publication No. 2001/0019782. Phosphorescent heavy metal organometallic complexes and their respective devices have also been the subject of International Patent Application Publications WO 00/57676, WO 00/70655, and WO 01/41512; and U.S. Ser. Nos. 0/9274,609, now abandoned; 09/452,346, now abandoned; 09/637,766; 60/283,814; and U.S. Ser. No. 09/978,455, filed Oct. 16, 2001, entitled xe2x80x9cOrganometallic Compounds and Emission-Shifting Organic Electrophosphorescencexe2x80x9d to Lamansky, et al.
Despite the recent discoveries of efficient heavy metal phosphors and the resulting advancements in OLED technology, there remains a need for even greater efficiency in devices. Fabrication of brighter devices that use less power and have longer lifetimes will contribute to the development of new display technologies and help realize the current goals toward full color electronic display on flat surfaces. The phosphorescent organometallic compounds, and the devices comprising them, described herein, help fulfill these and other needs.
In one aspect, the present invention provides compounds of Formula I, II, or III: 
wherein:
M is a metal atom;
each A1 and A2 is, independently, a monodentate ligand; or A1 and A2 are covalently joined together to form a bidentate ligand;
each R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 is, independently, H, F, Cl, Br, I, R11, OR11, N(R11)2, P(R11)2, P(OR11)2, POR11, PO2R11, PO3R11, SR11, Si(R11)3, B(R11)2, B(OR11)2, C(O)R11, C(O)OR11, C(O)N(R11)2, CN, NO2, SO2, SOR11, SO2R11, SO3R11; and additionally, or alternatively, any one or more of R1 and R2, or R2 and R3, or R3 and R4, or R5 and R6, or R6 and R7, or R7 and R8, or R9 and R10, together form, independently, a fused 4- to 7-member cyclic group, wherein said cyclic group is cycloalkyl, cycloheteroalkyl, aryl, or heteroaryl, and wherein said cyclic group is optionally substituted by one or more substituents X;
each R11 is, independently, H, C1-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C1-C20 heteroalkyl, C3-C40 aryl, C3-C40 heteroaryl; wherein R11 is optionally substituted by one or more substituents X;
each X is, independently, H, F, Cl, Br, I, R12, OR12, N(R12)2, P(R12)2, P(OR12)2, POR12, PO2R12, PO3R12, SR12, Si(R12)3, B(R12)2, B(OR12)2 C(O)R12, C(O)OR12, C(O)N(R12)2, CN, NO2, SO2, SOR12, SO2R12, or SO3R12;
each R12 is, independently, H, C1-C20 alkyl, C1-C20 perhaloalkyl C2-C20 alkenyl, C2-C20 alkynyl, C1-C20 heteroalkyl, C3-C40 aryl, or C3-C40 heteroaryl;
m is the formal charge of metal atom M;
n is 1, 2 or 3; and
wherein at least one of R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 is not H in compounds of Formula I.
In some embodiments, M can be a heavy metal. In further embodiments, M can be Ir, Os, Pt, Pb, Re, or Ru; or M can be Ir; or M can be Pt. In further embodiments, A1 and A2 can be monodentate ligands which, in turn, can have a combined charge of (xe2x88x921). In yet further embodiments, A1 or A2 can be F, Cl, Br, I, CO, CN, CN(R11), SR11 SCN, OCN, P(R11)3, P(OR11)3, N(R11)3, NO, N3, or a nitrogen-containing heterocycle optionally substituted by one or more substituents X. In further embodiments, A1 and A2 can be covalently joined together to form a bidentate ligand, which can be monoanionic. In some embodiments, the bidentate ligand can be 
According to further embodiments, the bidentate ligand can coordinate through a carbon atom and a nitrogen atom. Further, the bidentate ligand can be a biaryl compound. In some embodiments, the bidentate ligand can be 
wherein:
Z is O, S, or NR;
each R is, independently, R11; and
n is 0 to 5.
In some embodiments, bidentate ligand can be acetylacetonate.
In yet further embodiments, each R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 can be, independently, H, CH3, CF3, OCH3, or F. In other embodiments, at least one of R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 is methyl. In other embodiments, at least one of R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 is trifluorometnyl. In other embodiments, at least one of R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 is methoxy. In other embodiments, at least one of R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 is fluoro. In other embodiments, at least one of said R3, R4, R9, and R10 is other than H.
According to some embodiments, compounds of the present invention can have a photoluminescence maximum at a wavelength of from about 550 to about 700 nm.
The present invention further includes compositions comprising a compound of Formula I, II, or III as described above. Compositions can further comprise BCP, CBP, OXD7, TAZ, CuPc, NPD, Alq3, BAlq, FIrpic, or Irppy.
Also embodied by the present invention are compounds of Formula I 
wherein:
M is a metal atom;
each A1 and A2 is, independently, a monodentate ligand; or A1 and A2 are covalently joined together to form a bidentate ligand;
each R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 is, independently, H, an activating group, or a deactivating group; and additionally, or alternatively, any one or more of R1 and R2, or R2 and R3, or R3 and R4, or R5 and R6, or R6 and R7, or R7 and R8, or R9 and R10, together form, independently, a fused 4- to 7-member cyclic group, wherein said cyclic group is cycloalkyl, cycloheteroalkyl, aryl, or heteroaryl, and wherein said cyclic group is optionally substituted by one or more substituents X;
each X is, independently, H, F, Cl, Br, I, R12, OR12, N(R12)2, P(R12)2, P(OR12)2, POR12, PO2R12, PO3R12, SR12, Si(R12)3, B(R12)2, B(OR12)2C(O)R12, C(O)OR12, C(O)N(R12)2, CN, NO2, SO2, SOR12, SO2R12, or SO3R12;
each R12 is, independently, H, C1-C20 alkyl, C1-C20 perhaloalkyl C2-C20 alkenyl, C2-C20 alkynyl, C1-C20 heteroalkyl, C3-C40 aryl, or C3-C40 heteroaryl;
m is the formal charge of metal atom M;
n is 1, 2 or 3; and
wherein at least one of R3, R9, and R10 is an activating group, or wherein at least one of R3, R4, R9, and R10 is a deactivating group.
According to some embodiments of the compounds of Formula I, at least one of R3, R9, and R10 is an activating group. According to other embodiments of the compounds of Formula I at least one of R3, R4, R9, and R10 is a deactivating group. In some embodiments of the compounds of Formula I, activating groups can be alkyl, heteroalkyl, aryl, heteroaryl, alkoxy, aryloxy, hydroxy, mercapto, thiolato, amino, phosphino, alkylcarbonylamino, or arylcarbonylamino. In other embodiments of the compounds of Formula I, activating groups can be methyl or methoxy. According to some embodiments of the compounds of Formula I, deactivating groups can be halo, cyano, nitro, aldehyde, alkylcarbonyl, arylcarbonyl, ammonium, perhaloalkyl, carboxylic acid, alkoxycarbonyl, aryloxycarbonyl, or sulfo. In other embodiments of the compounds of Formula I, deactivating group can be F or CF3. In yet further embodiments of the compounds of Formula I, at least two of said R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 can be activating or deactivating groups.
Further embodiments of the compounds of Formula I include compounds where A1 and A2 are covalently joined together to form a bidentate ligand. The bidentate ligand can be monoanionic. The bidentate ligand can be acetylacetonate (acac), picolinate (pic), bexafluoroacetylacetonate, salicylidene, or 8-hydroxyquinolinate. In some embodiments, the bidentate ligand is acetylacetonate.
In yet further embodiments of the compounds of Formula I, M can be a heavy metal. In still further embodiments, M can be Ir, Os, Pt, Pb, Re, or Ru; or M can be Ir; or M can be Pt.
The present invention further includes compounds of Formula VI 
wherein:
M is a metal atom;
each A1 and A2 is, independently, a monodentate ligand; or A1 and A2 are covalently joined together to form a bidentate ligand; and
R4 is F; and R2, R3, R9, and R10 are each, independently, H, an activating group or deactivating group; or
R4 is OCH3; and R2, R3, R9, and R10 are each, independently, H, an activating group or deactivating group; or
R3 is OCH3; and R2, R4, R9, and R10 are each, independently, H, an activating group or deactivating group; or
R2 is OCH3; and R3, R4, R9, and R10 are each, independently, H, an activating group or deactivating group; or
R4 is CF3; and R2, R3, R9, and R10 are each, independently, H, an activating group or deactivating group; or
R3 is CF3; and R2, R4, R9, and R10 are each, independently, H, an activating group or deactivating group; or
R2 is CF3; and R3, R4, R9, and R10 are each, independently, H, an activating group or deactivating group; or
R2 and R4 are each F; and R3, R9, and R10 are each, independently, H, an activating group or deactivating group; or
R9 is CH3; and R2, R3, R4, and R10 are each, independently, H, an activating group or deactivating group; or
R10 is CH3; and R2, R3, R4, and R9 are each, independently, H, an activating group or deactivating group.
According to some embodiments of the compounds of Formula VI, A1 and A2 can be covalently joined together to form a bidentate ligand. In other embodiments of the compounds of Formula VI, the bidentate ligand can be monoanionic. In further embodiments of the compounds of Formula VI, bidentate ligand can be acetylacetonate (acac), picolinate (pic), hexafluoroacetylacetonate, salicylidene, or 8-hydroxyquinolinate. In yet further embodiments of the compounds of Formula VI, bidentate ligand can be acetylacetonate.
In some embodiments of the compounds of Formula VI, M can be a heavy metal; or M can be Ir, Os, Pt, Pb, Re, or Ru; or M can be Ir; or M can be Pt.
The present invention further includes compounds of Formula IV 
wherein:
R4 is F; and R2, R3, R9, and R10 are each H; or
R4 is OCH3; and R2, R3, R9, and R10 are each H; or
R3 is OCH3; and R2, R4, R9, and R10 are each H; or
R2 is OCH3; and R3, R4, R9, and R10 are each H; or
R4 is CF3; and R2, R3, R9, and R10 are each H; or
R3 is CF3; and R2, R4, R9, and R10 are each H; or
R2 is CF3; and R3, R4, R9, and R10 are each H; or
R2 and R4 are each F; and R3, R9, and R10 are each H; or
R4 and R10 are each CH3; and R2, R3, and R9 are each H; or
R9 is CH3; and R2, R3, R4, and R10 are each H; or
R10 is CH3; and R2, R3, R4, and R9 are each H.
In some embodiments of the compounds of Formula IV, R4 is F; and R2, R3, R9, and R10 are each H. In other embodiments of the compounds of Formula IV, R4 is OCH3; and R2, R3, R9, and R10 are each H. In other embodiments of the compounds of Formula IV, R3 is OCH3; and R2, R4, R9, and R10 are each H. In other embodiments of the compounds of Formula IV, R2 is OCH3; and R3, R4, R9, and R10 are each H. In other embodiments of the compounds of Formula IV, R4 is CF3; and R2, R3, R9, and R10 are each H. In other embodiments of the compounds of Formula IV, R3 is CF3; and R2, R4, R9, and R10 are each H. In other embodiments of the compounds of Formula IV, R2 is CF3; and R2, R4, R9, and R10 are each H. In other embodiments of the compounds of Formula IV, R2 and R4 are each F; and R3, R9, and R10 are each H. In other embodiments of the compounds of Formula IV, R4 and R10 are each CH3; and R2, R3, and R9 are each H. In other embodiments of the compounds of Formula IV, R9 is CH3; and R2, R3, R4, and R10 are each H. In other embodiments of the compounds of Formula IV, R10 is CH3; and R2, R3, R4, and R9 are each H.
The present invention further embodies compounds of Formula V 
The present invention further provides methods of increasing the wavelength of a photoluminescence maximum for compounds of the present invention, said methods comprising choosing substituents R1, R2, R3, R4, R5, R6, R7, R8, R9, or R10 such that at least one of said substituents is an activating group that influences the HOMO energy level of said compound, or at least one of said substituents is a deactivating group that influences the LUMO energy level of said compound.
The present invention further provides methods of decreasing the wavelength of a photoluminescence maximum for compounds of the present invention, said methods comprising choosing substituents R1, R2, R3, R4, R5, R6, R7, R8, R9, or R10 such that at least one of said substituents is a deactivating group that influences the HOMO energy level of said compound, or at least one of said substituents is an activating group that influences the LUMO energy level of said compound.
The present invention further includes organic light emitting devices comprising a compound of Formula I, II, or III 
wherein:
M is a metal atom;
each A1 and A2 is, independently, a monodentate ligand; or A1 and A2 are covalently joined together to form a bidentate ligand;
each R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 is, independently, H, F, Cl, Br, I, R11, OR11, N(R11)2, P(R11)2, P(OR11)2, POR11, PO2R11, PO3R11, SR11, Si(R11)3, B(R11)2, B(OR11)2, C(O)R11, C(O)OR11, C(O)N(R11)2, CN, NO2, SO2, SOR11, SO2R11, SO3R11; and additionally, or alternatively, any one or more of R1 and R2, or R2 and R3, or R3 and R4, or R5 and R6, or R6 and R7, or R7 and R8, or R9 and R10, together form, independently, a fused 4- to 7-member cyclic group, wherein said cyclic group is cycloalkyl, cycloheteroalkyl, aryl, or heteroaryl, and wherein said cyclic group is optionally substituted by one or more substituents X;
each R11 is, independently, H, C1-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C1-C20 heteroalkyl, C3-C40 aryl, C3-C40 heteroaryl; wherein R11 is optionally substituted by one or more substituents X;
each X is, independently, H, F, Cl, Br, I, R12, OR12, N(R12)2, P(R12)2, P(OR12)2, POR12, PO2R12, PO3R12, SR12, Si(R12)3, B(R12)2, B(OR12)2C(O)R12, C(O)OR12, C(O)N(R12)2, CN, NO2, SO2, SOR12, SO2R12, or SO3R12;
each R12 is, independently, H, C1-C20 alkyl, C1-C20 perhaloalkyl C2-C20 alkenyl, C2-C20 alkynyl, C1-C20 heteroalkyl, C3-C40 aryl, or C3-C40 heteroaryl;
m is the formal charge of metal atom M;
n is 1, 2 or 3; and
wherein at least one of R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 is not H in compounds of Formula I.
According to some embodiments, devices can have compounds of Formula I, Formula II, or Formula III. In other embodiments, device can include an emissive layer comprising one or more compounds of the present invention. In further embodiments, the emissive layer consists essentially of one or more compounds of the present invention. In other embodiments, the emissive layer can comprise host material doped with compounds of the present invention. In some embodiments, compound of the present invention comprise from about 1 to about 20 wt % of the emissive layer. In other embodiments, host material comprises BCP, CBP, OXD7, TAZ, CuPc, NPD, Alq3, or BAlq. In yet other embodiments, the emissive layer further comprises FIrpic or Irppy.
According to some embodiments, devices have an electroluminescence maximum of from about 550 to about 700 nm. In other embodiments, devices emit a color having color index coordinates (CIE) of from about 0.5 to about 0.8 for x and about 0.2 to about 0.5 for y. In yet further embodiments, devices have an external quantum efficiency greater than about 4% at a brightness greater than about 10 cd/m2. In other embodiments, devices have an external quantum efficiency greater than about 4% at a brightness greater than about 100 cd/m2.
In some embodiments, the present invention further provides organic light emitting devices comprising a compound of Formula I 
wherein:
M is a metal atom;
each A1 and A2 is, independently, a monodentate ligand; or A1 and A2 are covalently joined together to form a bidentate ligand;
each R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 is, independently, H, an activating group, or a deactivating group; and additionally, or alternatively, any one or more of R1 and R2, or R2 and R3, or R3 and R4, or R5 and R6, or R6 and R7, or R7 and R8, or R9 and R10, together form, independently, a fused 4- to 7-member cyclic group, wherein said cyclic group is cycloalkyl, cycloheteroalkyl, aryl, or heteroaryl, and wherein said cyclic group is optionally substituted by one or more substituents X;
each X is, independently, H, F, Cl, Br, I, R12, OR12, N(R12)2, P(R12)2, P(OR12)2, POR12, PO2R12, PO3R12, SR12, Si(R12)3, B(R12)2, B(OR12)2C(O)R12, C(O)OR12, C(O)N(R12)2, CN, NO2, SO2, SOR12, SO2R12, or SO3R12;
each R12 is, independently, H, C1-C20 alkyl, C1-C20 perhaloalkyl C2-C20 alkenyl, C2-C20 alkynyl, C1-C20 heteroalkyl, C3-C40 aryl, or C3-C40 heteroaryl;
m is the formal charge of metal atom M;
n is 1, 2 or 3; and
wherein at least one of R3, R9, and R10 is an activating group, or wherein at least one of R3, R4, R9, and R10 is a deactivating group.
In some such embodiments, at least one of R3, R9, and R10 is an activating group. In other such embodiments, at least one of R3, R4, R9, and R10 is a deactivating group. In further such embodiments, activating groups can be alkyl, heteroalkyl, aryl, heteroaryl, alkoxy, aryloxy, hydroxy, mercapto, thiolato, amino, phosphino, alkylcarbonylamino, or arylcarbonylamino. In yet further such embodiments, activating groups can be methyl or methoxy. According to some such embodiments, deactivating groups can be halo, cyano, nitro, aldehyde, alkylcarbonyl, arylcarbonyl, ammonium, perhaloalkyl, carboxylic acid, alkoxycarbonyl, aryloxycarbonyl, or sulfo. In other such embodiments, deactivating groups can be F or CF3. In yet further such embodiments, at least two of said R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 are activating or deactivating groups.
According to some such embodiments, A1 and A2 can be covalently joined together to form a bidentate ligand. In some such embodiments, bidentate ligand can be monoanionic. In some such embodiments, bidentate ligand can be acetylacetonate (acac), picolinate (pic), hexafluoroacetylacetonate, salicylidene, or 8-hydroxyquinolinate. In some embodiments, bidentate ligand is acetylacetonate.
According to some such embodiments, M can be a heavy metal. In other such embodiments, M can be Ir, Os, Pt, Pb, Re, or Ru; or M can be Ir; or M can be Pt.
In some such embodiments, devices can include an emissive layer comprising compounds of the present invention. In some such embodiments, the emissive layer consists essentially of compounds of the present invention. In other such embodiments, the emissive layer comprises host material doped with compounds of the present invention. In further of such embodiments, compounds of the present invention can comprise from about 1 to about 20 wt % of the emissive layer. In some such embodiments, host material comprises BCP, CBP, OXD7, TAZ, CuPc, NPD, Alq3, or BAlq. In other such embodiments, the emissive layer further comprises FIrpic or Irppy.
According to some such embodiments, devices can have an electroluminescence maximum of from about 550 to about 700 nm. In other embodiments, color emitted from such devices can have color index coordinates (CIE) of from about 0.5 to about 0.8 for x and about 0.2 to about 0.5 for y. In some embodiments, such devices can have an external quantum efficiency greater than about 4% at a brightness greater than about 10 cd/m2. In other such embodiments, such devices can have an external quantum efficiency greater than about 4% at a brightness greater than about 100 cd/m2.
Further embodiments of the present invention include organic light emitting devices comprising compounds of Formula VI 
wherein:
M is a metal atom;
each A1 and A2 is, independently, a monodentate ligand; or A1 and A2 are covalently joined together to form a bidentate ligand; and
R4 is F; and R2, R3, R9, and R10 are each, independently, H, an activating group or deactivating group; or
R4is OCH3; and R2, R3, R9, and R10 are each, independently, H, an activating group or deactivating group; or
R3 is OCH3; and R2, R4, R9, and R10 are each, independently, H, an activating group or deactivating group; or
R2 is OCH3; and R3, R4, R9, and R10 are each, independently, H, an activating group or deactivating group; or
R4 is CF3; and R2, R3, R9, and R10 are each, independently, H, an activating group or deactivating group; or
R3 is CF3; and R2, R4, R9, and R10 are each, independently, H, an activating group or deactivating group; or
R2 is CF3; and R3, R4, R9, and R10 are each, independently, H, an activating group or deactivating group; or
R2 and R4 are each F; and R3, R9, and R10 are each, independently, H, an activating group or deactivating group; or
R9 is CH3; and R2, R3, R4, and R10 are each, independently, H, an activating group or deactivating group; or
R10 is CH3; and R2, R3, R4, and R9 are each, independently, H, an activating group or deactivating group.
According to some such embodiments, A1 and A2 can be covalently joined together to form a bidentate ligand. In other such embodiments, bidentate ligand can be monoanionic. In some such embodiments, bidentate ligand is acetylacetonate (acac), picolinate (pic), hexafluoroacetylacetonate, salicylidene, or 8-hydroxyquinolinate. In yet other such embodiments, bidentate ligand can be acetylacetonate.
In some such embodiments, M can be a heavy metal; or M can be Ir, Os, Pt, Pb, Re, or Ru; or M can be Ir; or M can be Pt.
The present invention further includes organic light emitting devices comprising compounds of Formula IV 
wherein:
R4 is F; and R2, R3, R9, and R10 are each H; or
R4 is OCH3; and R2, R3, R9, and R10 are each H; or
R3 is OCH3; and R2, R4, R9, and R10 are each H; or
R2 is OCH3; and R2, R4, R9, and R10 are each H; or
R4 is CF3; and R2, R3, R9, and R10 are each H; or
R3 is CF3; and R2, R4, R9, and R10 are each H; or
R2 is CF3; and R3, R4, R9, and R10 are each H; or
R2 and R4 are each F; and R3, R9, and R10 are each H; or
R4 and R10 are each CH3; and R2, R3, and R9 are each H; or
R9 is CH3; and R2, R3, R4, and R10 are each H; or
R10 is CH3; and R2, R3, R4, and R9 are each H.
In some such embodiments, R4 is F; and R2, R3, R9, and R10 are each H. In other such embodiments, R4 is OCH3; and R2, R3, R9, and R10 are each H. In other such embodiments, R3 is OCH3; and R2, R4, R9, and R10 are each H. In other such embodiments, R2 is OCH3; and R3, R4, R9, and R10 are each H. In other such embodiments, R4 is CF3; and R2, R3, R9, and R10 are each H. In other such embodiments, R3 is CF3; and R2, R4, R9, and R10 are each H. In other such embodiments, R2 is CF3; and R3, R4, R9, and R10 are each H. In other such embodiments, R2 and R4 are each F; and R3, R9, and R10 are each H. In other such embodiments, R4 and R10 are each CH3; and R2, R3, and R9 are each H. In other such embodiments, R9 is CH3; and R2, R3, R4, and R10 are each H. In other such embodiments, R10 is CH3; and R2, R3, R4, and R9 are each H.
The present invention further includes organic light emitting devices comprising compounds of Formula V 
The present invention further provides methods of increasing the wavelength of an electroluminescence maximum of an organic light emitting device comprising one or more compounds of the present invention, said methods comprising choosing substituents R1, R2, R3, R4, R5, R6, R7, R8, R9, or R10 such that at least one of said substituents is an activating group that influences the HOMO energy level of said compound, or at least one of said substituents is a deactivating group that influences the LUMO energy level of said compound.
The present invention further provides methods of decreasing the wavelength of an electroluminescence maximum of an organic light emitting device comprising one or more compounds of the present invention, said methods comprising choosing substituents R1, R2, R3, R4, R5, R6, R7, R8, R9, or R10 such that at least one of said substituents is a deactivating group that influences the HOMO energy level of said compound, or at least one of said substituents is an activating group that influences the LUMO energy level of said compound.
The present invention also provides pixels comprising devices of the present invention.
The present invention also provides electronic displays comprising devices of the present invention.